What is your perception of smart-casual? What consultancy are you having the interview? If they say smart-casual, then why would you turn up in a suit?? Don't turn up in a suit if they want you to turn up in smart-casual. In my experience, if you did, even after I have specifically asked you to be smart-casual, then I'm going to be thinking this guy/gal can't "let her/his hair down" and is a right ... Wear a clean ironed shirt, pressed trousers and buffed shoes. Leave the tie at home, the beer cufflinks and multi-coloured socks. Sounds plain, but that is smart but casual. Leave the jacket/coat, unless it is wet/windy. Have a leather binder holding only a notepad, a working pen and your updated CV. Hope this helps.